Satisfactory results of a psychometric analysis and calculation of minimal clinically important differences of the World Health Organization quality of life-BREF questionnaire in an observational cohort study with lung cancer and mesothelioma patients

BACKGROUND: To determine the psychometric properties and minimal clinically important differences (MCIDs) of the World Health Organization Quality of Life-BREF (WHOQOL-BREF) in advanced stage lung cancer patients. METHODS: Patients (n = 153) completed the WHOQOL-BREF and the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30). Confirmatory factor analysis (CFA) was performed and reliability and construct validity determined. MCIDs were estimated with two distribution-based methods (0.5 standard deviation (SD) and 1 standard error of measurement (1 SEM)). RESULTS: CFA confirmed WHOQOL-BREF domain structure. All domains demonstrated good internal consistency (α > 0.70), except Social Relationships (α = 0.57). Nineteen of the 24 WHOQOL-BREF items had correlations of ≥ 0.40 with their intended domain. Four items had higher correlations with a domain other than their intended domain. Moderate to strong correlations were observed for corresponding domains of the two questionnaires, except for the social domains (r = 0.07). For 0.5 SD, MCIDs ranged from 0.88 to 1.55, and for 1 SEM MCIDs ranged from 1.76 to 2.72. CONCLUSIONS: The WHOQOL-BREF has satisfactory psychometric properties in patients with advanced stage lung cancer, whereas the observed MCIDs provide a method for interpretation of scores.